The GeoJSON standard defines a geospatial interchange format based on the JavaScript Object Notation (JSON).
This format is suited to web-based applications and it can provide
a format that is more concise and easier to interpret than WKT or WKB. See
http://geojson.org/geojson-spec.html.

The ST_AsGeoJSON method returns a text string representing the geometry.
A number of different text formats are supported (with associated options) and the desired format
is selected using the optional format parameter.
If the format parameter is not specified, the default is 'GeoJSON'.

The format string defines an output format and parameters to the format.
The format string has one of the following formats:

format-name

format-name(parameter1=value1;parameter2=value2;...)

parameter1=value1;parameter2=value2;...

The first format specifies the format name and no parameters. All format parameters use their default values.
The second format specifies the format name and a list of named parameter values. Parameters that are not supplied use their
default values.
The last format specifies only parameter values, and the format name defaults to 'GeoJSON'.